This invention relates to a measurement system having an analyzer unit and at least one replaceable sensor, each sensor having a transponder in which sensor-specific data is stored, and the analyzer unit having an antenna for wireless readout of the data stored in the transponder and for wireless transmission of the power required to operate the transponder.
Sensor-specific data stored in the transponder may include, for example, information on the measurement range, calibration data, the manufacturing date (in the case of aging-sensitive sensors), identification numbers, which prevent inadvertent connection of sensors not approved for use with the analyzer, and similar data.
Measurement systems of this type are known, for example, from German Patent Application 197 22 744 A1, which is incorporated into the present application by reference. In the measurement system described there, the sensor is connected to the analyzer unit by a plug-and-socket connection, which transmits the measurement signal of the sensor to the analyzer unit. The transponder is situated on the sensor in the vicinity of this. plug-and-socket connection, and the antenna is situated on the analyzer unit for readout. However, the plug-and-socket connection is a weak point, in particular when low voltages must be transmitted—e.g., in the case of load cells with wire strain gauges—whereby thermal stresses result in significant errors. Such plug-and-socket and-socket connections are also disadvantageous when the sensors deliver a very high-impedance signal—e.g., pH electrodes—and are therefore susceptible to contact problems and insulation resistance is inadequate. Finally, plug-and-socket connections are preferably avoided also when the sensors are replaced frequently, which increases the risk of wear and breakage.